To apply a liquid such as a photoresist liquid to a surface of an applied member of a semiconductor wafer or glass board from an application nozzle, a liquid supply device has been used. As the liquid supply device utilized for above use applications, there is a drive pump in form of reciprocating an elastically deformable pump member axially by a drive rod. The drive rod is mounted axially reciprocably in a cylindrical housing, and the elastically deformable pump member is provided axially between a tip portion of the drive rod and the housing, and a pump chamber, i.e., a drive chamber that is expandable and contractible by the pump member is formed in the housing. As the pump member, there are in form of a bellows as disclosed in Japanese Patent Application Laid-Open Publication No. 7-310838, and in the form of a diaphragm as disclosed in Japanese Patent Application Laid-Open Publication No. 8-170744.
The liquid supply devices comprising the drive pumps having structures disclosed in above Patent Documents have supplied a liquid such as a chemical liquid to the applied members directly from the pump chambers that are expanded and contracted by the drive rods. In contrast, for example, disclosed in Japanese Patent Application Laid-Open Publication No. 11-230048 is a liquid supply device of an indirect operation type in which a liquid supply pump, which is provided with a flexible tube that is also called a tubephragm and partitions a pump chamber and a drive chamber, is driven by the drive pump having the above-mentioned form. In the liquid supply device having the above form, the liquid pump is driven indirectly by supplying the liquid to the drive chamber of the liquid supply pump from the pump chamber.
As a drive pump in form of using the bellows, Japanese Patent Application Laid-Open Publication No. 2007-315295 discloses expanding and contracting the bellows to perform a pump operation by supplying gas into the bellows. In the drive pump, to prevent the bellows from deforming inwardly in expanding and contracting the bellows, a restriction member is incorporated into the bellows. Also, in a drive pump in form of a bellows as disclosed in Japanese Patent Application Laid-Open Publication No. 2005-83250, an annular bellows protecting member is attached outside the bellows driven for expansion and contraction by the drive rod, whereby a deformation of an accordion-shaped portion is prevented.
In a pre-processing step of manufacturing semiconductors or liquid crystal panels, the liquid supply device with the above form is used to discharge a liquid such as a photoresist liquid onto semiconductor wafers and glass substrates. The liquid received in a liquid container is sucked by the liquid supply device, and discharged from an applying nozzle. Included in configurations of pumps is a syringe type in addition to the above-mentioned bellows, diaphragm, and tube types. The liquid supply devices used for those types demand chemical resistance for preventing corrosion due to the liquid, and a portion or region contacting with the liquid is mainly made of a fluorocarbon resin, stainless steel, or a ceramics. Further, to apply the liquid to the applied members with uniform thickness to decrease or eliminate product defects such as circuit pattern hiatuses, the liquid supply devices having cleanliness properties and low dust-generating properties are important.
In the liquid supply devices of the bellows and diaphragm types, particularly, since the pump members are elastically deformed at discharge and suction operation times, chemical resistance as well as flexibility are needed for the pump members and, therefore, fluorocarbon resins are selected.
In a step of applying the liquid, pressures in a pump chamber and liquid are generated during discharging and sucking operations by influences due to various conditions such as device or piping conditions, viscosity of the liquid, and discharge flow rates. Since the pump member comprising the bellows or diaphragm made of a fluorocarbon resin is made of an elastic material, when a discharge pressure in discharging the liquid is high, such a pump member is deformed in a direction in which a diameter of the pump member contracts due to a discharge load applied to the pump member. Meanwhile, when a suction negative pressure in sucking the liquid is high, the pump member is deformed in a direction in which the diameter expands due to a suction load applied to the pump member. Consequently, the pump chamber does not expand and contract based on a volume change amount corresponding to a stroke of a drive rod, whereby variations in shortage and accuracy of a discharge amount of the liquid occur. Further, exertion of a high pressure onto the pump member causes deformation, deterioration, and breakage of the pump member comprising the bellows or diaphragm, etc. In the long term, the exertion becomes a factor of deterioration of life time of the liquid supply device.
Deformation of the pump member such as a bellows does not cause the variations in the accuracy of the discharge amount but also make various influences on a delay of a flow rising at a discharge starting time, a flow fluctuation during the discharge, and so on. As a result, thicknesses of layers of the liquids applied to surfaces of the semiconductor wafers become non-uniform, and manufacture yields of semiconductor products are reduced. In an actual semiconductor manufacturing process, to reduce the influence on the flow fluctuation of the liquid discharged from the liquid supply device, drive speed needs to be controlled according to a discharge flow characteristic, and a program recipe for actuating the liquid supply device may be made complicated. Meanwhile, after the liquid is applied thicker than necessary, when the surplus liquid is caused to fly apart for obtaining a desired thickness of the applied liquid, the liquid used becomes waste, and inefficiency on the manufacture and cost rise are difficult to avoid.
The most ideal discharge characteristic of the liquid supply device is to have a rapid rising of the discharge flow at a time of the discharge start, and a discharging operation with a constant flow and without flow fluctuation.
However, the discharge pressure becomes some causes actually, and this influences the discharge accuracy or quality of manufactured products, so that drive conditions of the liquid supply device are restricted depending on pumping performance. Since safety margins regarding pressure resistance performance of the pump are taken, the pump must be used at a low pressure level. For this reason, production under the ideal conditions is difficult, and the life time of the pump is also influenced by conditions of discharged pressures. Consequently, it is not too much to say that limitations on production efficiency and production costs are limited to the pump performance.
The flexible pump member such as bellows and diaphragm is generally a member requiring flexibility as a function, and also need rigidity. Consequently, the pump member requires incompatible performance. However, it is actually difficult at present to obtain the flexibility and rigidity simultaneously.
In contrast, the pump of the syringe type is superior regarding rigidity and pressure resistance performance. The syringe type is in form of pressurizing a liquid by a piston, and has a high pressure resistance performance, so that an influence of the discharge accuracy due to the pressure load is small. However, the piston is in slidable contact with an inner circumferential face of a cylinder, as a result of which occurrence of abrasive powder, i.e., particles from a sliding portion is not avoided, and there is a fear of occurrences of contamination and leakage, etc. of the liquid due to the particles. Accordingly, use of the syringe type pump in a semiconductor manufacturing process involves a very high risk. This needs to do frequent maintenance for inspecting the sliding portion. Therefore, life time of driving the syringe type pump is shorter than other type pumps, and there is a problem in that use efficiency such as maintenance costs or low operation rates due to stop of the manufacturing process is bad. Consequently, this type pump is hardly used in the semiconductor manufacturing process.
An object of the present invention is to improve discharge accuracy of a liquid supply device having a flexible pump member such as a bellows.
Another object of the present invention is to improve durability of the liquid supply device.